Cooldown reduction (abbreviated as CDR) is a champion statistic that reduces the cooldown of abilities, or the amount of time you must wait before an ability can be used again once you activated it, by a percentage.

Cooldown reduction is granted by items, buffs, runes and masteries, as well as some passive abilities.

Cooldown reduction works additively. If you have a 6% cooldown reduction from masteries, and a 10% cooldown reduction from Stinger you will have a 16% cooldown reduction. Cooldown reduction cannot be increased beyond 40% by absolutely any means.

Some champions have abilities that decrease their cooldowns by a flat amount, either their base cooldown or current cooldown, or entirely refresh their cooldown. Base reduction occurs before cooldown reduction takes effect while flat reduction occurs after cooldown reduction takes effect. By using those, a champion can disregard the 40% cooldown reduction cap.

Note: Only the cooldown reduction of these abilities is shown here, to read more information on each of these abilities, follow the link on each of them.

卡特琳娜的Voracity reduces all her abilities' cooldowns by 15 seconds whenever she gets a kill or an assist.

魔腾的Umbra Blades innate cooldown is reduced by 1 second for every autoattack.

奥拉夫的Undertow cooldown is reduced by 4.5 seconds if he manages to pick up his axe after using the ability.

瑞兹的Arcane Mastery allows him to reduce all of his other abilities' cooldowns by 1 when he uses an ability.

慎的Ki Strike cooldown is reduced by 1.5 seconds every time Shen autoattacks, or by 3 seconds every time Shen autoattack while Feint's shield is up.

希瓦娜的Twin Bite cooldown is reduced by 0.5 seconds for every autoattack.

斯卡纳的Energize allows Skarner to reduces all of his abilities' cooldowns by 1 second for each successful autoattack on an enemy champion and 0.5 seconds for each successful autoattack on a non-champion target.

塔里克的Imbue cooldown is reduced by 1 for every autoattack and 3 seconds with every autoattack on a champion.